1. Field of the Invention
The present invention relates to a throttle body which controls air flow supplied to an engine in the fuel injection apparatus, and more particularly relates to a throttle control apparatus used for a motorcycle.
2. Description of the Conventional Art
A conventional throttle body will be described hereinafter with reference to FIGS. 4 and 5 in which FIG. 4 is a longitudinal section of the throttle body and FIG. 5 is a right side view of FIG. 4.
In the figures, the reference numeral 10 indicates a throttle body having an intake passage 11 extending through laterally therein. A throttle valve shaft 12 is provided, across the intake passage 11, and both ends of the throttle valve shaft 12 are rotatably supported on the throttle body 10.
Also, a throttle valve 13 is provided in the intake passage 11 for opening or closing of the intake passage 11. The throttle valve 13 is mounted on the throttle valve shaft 12 so as to open or close the intake passage 11 in accordance with the rotation of the throttle valve shaft 12.
One end 12a of the throttle valve shaft 12 is protruded rightward from one side outer wall 10a of the throttle body 10 (right side as shown in FIG. 4), and a drive lever 14 is mounted integrally with the one end 12a. 
The reference numeral 15 indicates a rotary shaft provided uprightly on the one side outer wall 10a of the of the throttle body 10. A throttle lever 16 is fixed to the rotary shaft 15 by means of a screw nut.
As shown in FIG. 5, the throttle lever 16 is provided with a first retention hole 16a and a second retention hole 16b. An end 17b, which is attached to one end of the accelerator wire 17a to make the throttle valve 13 open, is inserted to the first retention hole 16a and engaged therein, while an end 17d, which is attached to one end of the accelerator wire 17c to make the throttle valve 13 close, is inserted to the second retention hole 16b and engaged therein.
Other ends of the accelerator wires 17a and 17c are connected to the acceleration grips (not shown) respectively. When the acceleration grip is rotated by a driver, this rotation is transmitted to the throttle lever 16 through the ends 17b and 17d of the accelerator wires 17a and 17c, respectively, to rotate the throttle lever 16.
The reference numeral 18 indicates a link lever which connects the throttle lever 16 and the drive lever 14. The rotation of the throttle lever 16 is transmitted to the drive lever 14 through the link lever 18. Due to the arrangement where the throttle lever 16 and the drive lever 14 are connected by means of the link lever 18, the rotation of the acceleration grip and the opening characteristic of the throttle valve 13 are made nonlinear.
The reference numeral 19 indicates a throttle opening sensor attached to another end 12b of the throttle valve shaft 12 which protrudes from the other side outer wall 10b of the throttle body 10. The output signal from the opening sensor 19 is inputted to ECU (not shown) and is used for the various control.
When the acceleration grip (not shown) is rotated in one direction, a wire 17a to open the throttle valve 13 rotates the throttle lever 16 in a counterclockwise direction in FIG. 5. By this rotation, the drive lever 14 is rotated through link lever 18, resulting in the opening of the intake passage 11 by the throttle valve 13.
On the other hand, when the acceleration grip (not shown) is rotated in the other direction, a wire 17c to close the throttle valve 13 rotates the throttle lever 16 in a clockwise direction in FIG. 5. By this rotation, the drive lever 14 is rotated through link lever 18, resulting in the closing of the intake passage 11 by the throttle valve 13.
In the conventional throttle body, control of idling air flow rate at the time of idling of engine and/or control of initial air flow rate at the time of starting of engine are carried out by a bypass air control apparatus which comprises a bypass air passage that by-passes the throttle valve, and an air valve for controlling the opening area of the bypass air passage.
Generally, in the throttle body used for a motorcycle, the air valve is remote operated by a initial operation wire which is connected to a start lever. The start lever is arranged in the neighborhood of the acceleration grip and is operated by the driver. Two kinds of wires are arranged around the throttle body, i.e. two accelerator wires and one initial operation wire.
In the conventional throttle body used for the motorcycle, there are problems that the two kinds of wires should be arranged without interfering one another, and the bypass air control apparatus should be arranged in close vicinity to the peripheral wall of the throttle body in order to make the throttle body compact.